This application claims the right of foreign priority to Application No. 100 07 024.8 filed in Germany (B.R.D.) on Feb. 16, 2000, and to Application No. 00 116 128.0 filed in Germany (B.R.D.) on Jul. 31, 2000, and both applications are incorporated herein by reference in their entirety.
The invention relates to an automated cell for handling parts received in part carriers comprising a working space closed to the outside in which first, second, and third stack positions are arranged in sequence. The first stack position can be separated from the others to be secured against contact. The automated cell includes a transfer device having a first linear axis extending in horizontal direction along the sequentially arranged stack positions as well as a second linear axis coupled thereto extending in vertical direction, where the transfer device allows movement of part carriers in the horizontal direction and in the vertical direction as well as a positioning of the part carriers for an associated transfer unit. The transfer unit allows the removal of parts from the part carriers and the transfer to an external station outside the working space as well as the introduction of parts into the working space and placement into the part carriers. The first stack position can be loaded through a door from the outside in the first horizontal direction.
Such an automated cell is disclosed in EP 0 865 869 A1. The known automated cell comprises a pallet transferring device within a working space closed to the outside, which can stack and unstack workpiece carriers between the two stack positions and additionally place them upwardly in a third intermediate position, so that individual parts can be removed with a portal gripper from a transversely running portal thereabove and other parts can be placed therein. A stack exchange module is also provided with a rotary table to supply stacks of part carriers into a front loading space, while individual part carriers can be handled within the working space closed off to the loading space. The rotary table is pivoted by 180xc2x0 to introduce a stack of part carriers with fresh parts into the working space and to remove another stack of processed parts out of the space.
The construction of such automated cells is relatively complicated, because a stack exchange module must be provided apart from the pallet handling device. In addition, the space requirement of the automated cell is relatively large.
A further disadvantage arises when a so-called xe2x80x9cstack specific logisticsxe2x80x9d is desired, i.e. when a mixing of parts from a stack of carriers with parts from another stack of carriers should be avoided. In such a case, relative long idle times and exchange times are necessary.
Another handling apparatus is known from DE 198 05 206 A1, where three stack positions are provided sequentially within a closed working space close, between which a stack of workpiece carriers can be transferred back and forth on their roller carts. The stacks of workpiece carriers are pushed into the corresponding stack positions from the sides and are removed therefrom. A handling unit accepts the workpiece carriers in a receiving position and after processing places them in a discharging position. Protective walls can be moved in between the individual stacks of workpiece carriers to improve working safety.
The required supply and removal of stacks of workpiece carriers into or out of the apparatus from the side has proven to be a disadvantage. This leads to an increased space requirement and, in addition, it is not apparent that complete work safety can be ensured by only inserting protective walls.
A further disadvantage is that the movement of the stacks of workpiece carriers within the apparatus takes place on roller carts. This leads to the functional reliability depending on the floor properties and alignment and, especially for relatively heavy stacks of workpiece carriers, to slippage of the entire stack or individual workpiece carriers, which can strongly impair the functional reliability and the accuracy in positioning during handling. Thus the known apparatus is hardly suitable as an automated cell for an automatic or at least partially automated production operation.
It is a first object of the present invention to provide an improved automated cell for handling parts received on part carriers.
It is a further object of the present invention to provide an improved automated cell having a cost-inexpensive construction with the lowest possible space requirement.
It is still a further object of the invention to provide an improved automated cell allowing a flexible operation in handling the parts within a working space closed to the outside to be secure against contact.
It is still another object of the invention to provide high precision in the handling operations to be achieved.
Another object of the invention is to provide for a method for handling parts in an automated cell, which allows a flexible control.
Also stack-specific logistics should be possible as well as a rapid throughput of parts.
These and other objects are achieved according to the present invention with an automated cell of the above-mentioned type in that the first stack position is separated from the second stack position by a bulk head extending substantially vertical. Thus any contact of an operator with parts handled inside the automated cell is avoided.
Preferably, a hood is provided to separate the first stack position against the remaining part of the working space. The hood may be displaced between the first and second stack positions or between the first, second and third stack positions.
The object of the present invention is also achieved with a method for handling parts in an automated cell in which first, second and third stack positions are arranged sequentially in horizontal direction within a closed working space and in which part carriers for receiving the parts are re-stacked among the three stack positions by a transfer device. The parts are removed from the part carriers by a transfer unit, transported to a associated station, preferably a processing station outside of the working space and parts are taken up from the associated station and placed into the part carriers.
Stacks of part carriers with fresh parts are supplied in horizontal direction to the first stack position and stacks of part carriers with processed parts at the first stack location are removed from the working space in the opposing direction. Part carriers are lifted above a bulkhead extending substantially vertically between the first stack position and the second adjacent stack position and are moved in horizontal direction.
According to the invention, an automated cell with three sequential stack positions is provided in which the transfer of part carriers in the closed working space between the individual stack positions as well as the preparation of the part carriers for an associated transfer unit can be achieved with a single transfer device. The transfer unit can be a portal gripper driveable along a portal running above the automated cell.
In this manner, the construction of the automated cell is distinctly simplified and can be realized with a very small space requirement. With a special strategy for transferring part carriers between the individual stack positions, a rapid operation and good adaptation to the associated processing stations is realized with very short cycle times. The first stack position in combination with the hood, which is driveable at least between the first and second stack position, is separated to be secured against contact with respect to the remaining portion of the working space through the arrangement of a bulkhead between the first and second stack position. In this manner, part carriers can be moved between the second and third stack position, while at the same time a stack of part carriers can be supplied at the first stack position or removed therefrom. Despite the extremely simple configuration of the automated cell, a decoupling of the handling within the working space is ensured in this manner from the loading and unloading of the automated cell when the door is opened. In addition, a greater precision in handling results because the part carriers are not shifted on the roller carts within the working space, but are moved by the transfer device.
With this concept, a particularly simple and inexpensive as well as space-saving construction results. Such an automated cell can also be advantageously employed in combination with an interlinked production system, by which a plurality of automated cells are arranged as buffers between the different processing stations, where the transport of parts between the individual stations and the cells takes place by grippers driveable on the portals.
In an advantageous embodiment of the present invention, the bulkhead is configured to be stationary. This results in a particularly simple and space-saving construction, where the part carriers are lifted over the bulkhead for transfer between the first and second stack positions. For the purposes of service, the bulkhead wall is relatively simple to remove to allow a simple access to the working space of the cell.
In an additional embodiment of the present invention, the bulkhead is provided with centering surfaces for guiding and centering the part carriers supplied to the first stack position. In addition, guide elements can be associated with the bulkhead, which are arranged to engage the supplied part carriers from the side for centering.
Guide tracks can be provided in the region of the first stack location, which are preferably provided with adjustment elements for receiving the workpiece carriers from the roller carts in a defined end position. The guide tracks can be formed as supports upon which rollers are arranged.
With this feature, it can be ensured that stacks of part carriers which are not uniformly stacked, as can be the case for example with parts coming from a hardening plant, are properly centered when driven into the first stack position and are aligned with the bulkhead wall. This results in a defined end position. Thus an optimal positioning of the part carriers at the first stack position results on the whole, which leads to high accuracy in the subsequent handling and avoids errors in handling.
In an advantageous embodiment of the present invention, the hood is configured to be U-shaped with a cover surface and two side surfaces. This results in a simple construction, where suitable drive and guide means can be arranged for the hood at the lower region of the side surfaces. Preferably, the hood is arranged to be driveable between the first, second and third stack position. This results in greater flexibility in handling the parts or part carriers within the working space.
The hood can be driven by means of the transfer device. Alternatively, the hood can have its own driving device, which allows a positioning above the first, second or third stack position. In this manner, dead times are avoided which could arise when the hood is driven by the transfer device. Short cycle times are also realizable, which are determined by the external processing stations.
When even shorter cycle times are required, the hood itself can be configured to have at least one part carrier on its upper side. In this manner, the hood can be driven to the third stack position while the transfer device transfers part carriers between the first and second stack position.
A drawer for receiving a part carrier can also be provided on the upper side of the hood, which allows the part carrier to be driven to the outside when the operating door is opened. This enables the supply and discharge of test parts and also allows an operation of the cell with only one part carrier independent of the part carriers stored therein. For example a short series production run can be interposed in the working flow.
A shaft rotatable about its axis can be provided to lock the hood in the three positions above the first, the second or the third stack position. The shaft can be provided with locking pins which are lockable with pin recesses on the hood in predetermined positions. A simple configuration for locking the hood results.
The horizontal linear axis of the transfer device is preferably formed on a U-shaped frame, on which horizontal guides are provided at the two elongate sides, between which a gripping device for handling a part carrier is mounted to be driveable in the direction of the shanks, where the horizontal guides are each mounted on a vertical guide driveable in vertical direction. A particularly simple and stable construction of the transfer device results, where it is also possible to integrate the drive and guides of the vertical axis into a vertical support of the automated cell, which is a portion of the stable frame on which the cell is mounted.
This stable frame, which can consist of a central floor portion, a front vertical frame portion in the region of the door and a back frame portion, allows a compact construction and at the same time, the upper ends of the front and back frame portions can serve as support surfaces for the portals lying thereon.
In an advantageous embodiment of the present invention, the first stack position of the automated cell is closed to the outside by at least one operating door to be secure against contact, through which the part carriers are supplied and removed from the automated cell. A mechanical lock is formed between the at least one operating door and the hood, which only allows the at least one door to be opened when the hood is located above the first stack position. The electrical security system with limit switches, which is otherwise necessary for the operating door can be relinquished, which leads to a distinct savings in cost. In addition, the operation reliability is increased because the limit switches which can be subject to defect are no longer necessary.
In a further embodiment of the present invention, a service door is provided at the end surface of the automated cell in the region of the first stack position, which is pivotally mounted at the side of at least one vertical side of the front frame portion. At least one operating door is provided on the service door.
In this manner, the entire automated cell is accessible from the outside when the service door is open, so that service work can be easily carried out. The service door is pivotally mounted on either the right vertical side of the front frame or on the left vertical side or on both vertical sides. It is mechanically locked so that the service door can only be opened with a tool, e.g. an Allen key. An additional electric locking system with limit switches is not required.
With the method according to the present invention, a stack-specific logistics can be realized in simple manner, by which all of the parts of a stack of part carriers are placed back into the same stack again after processing.
In an advantageous embodiment of this method, only a portion of the fresh parts are removed from one part carrier and exchanged with finished parts from the associated station during at least one restacking procedure of the stack of part carriers from one stack position to another stack position. In addition, the remaining fresh parts in part carriers are exchanged with finished parts from the associated station during at least one restacking procedure to fill up the respective part carrier with finished parts.
With these features, delays caused by restacking the part carriers can be avoided, or not all parts of a part carrier are used in sequence and transfered to the associated processing station. Rather, at least one part is saved, so that one fresh part remains on each part carrier which can be used when later restacking and exchanged with a finished part.
The automated cell can be advantageously operated according to the present method, such that practically no delays result in the supply to the associated processing or assembling stations, despite having only a single transfer device with two linear axes.
A further advantage is that a so-called refreshing of the parts in the automated cell (xe2x80x9crefreshing a bufferxe2x80x9d) can be carried out without great effort, i.e. an exchange of the parts remaining in the automated cell over a longer time with new parts. An operation according to the FIFO principle (first in/first out) is also possible.
It will be understood that the above described features and those to be discussed below are applicable not only in the given combinations, but may be used in other combinations or taken alone without departing from the scope of the invention.